A dent you should worry about. Bars are under a lot of stress and I hate to imagine one breaking at the wrong time. Many manufacturers say that we are to consider them "consumables', which is to say they should be replaced sooner rather than later. Personally, I think that as long as the bar is not bent, the aluminum should still be sound enough to trust.

What you have there is a scratch. And a scratch in a good place. It is under the clamp, and so it is not under any particular stress.